/etc/logcheck/ignore.d.server/anon-proxy is in logcheck-database 1.3.17.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | ^\w{3} [ :0-9]{11} [._[:alnum:]-]+ AnonMix: \[[0-9]+/[0-9]+/[0-9]+-[:0-9]+, info +\] +Try connecting to next Mix\.\.\.$
^\w{3} [ :0-9]{11} [._[:alnum:]-]+ AnonMix: \[[0-9]+/[0-9]+/[0-9]+-[:0-9]+, info +\] +connected\!$
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